The minicolumn is an anatomical and functional unit of the brain whose genesis accrues from germinal cell divisions in the ventricular zone of the brain. Disturbances in the morphometry of minicolumns have been demonstrated recently for both autism and Down's syndrome. We report minicolumnar abnormalities in the brain of a dyslexic patient. The corresponding developmental disturbance (ie, large minicolumns) could account for the perceptual errors observed in dyslexia.